高压直流圆环形接地极电位数值模拟及影响因素分析

Potential Numerical Simulation and Analysis of Influencing Factors of Toroidal HVDC Grounding Electrode

在远距离高压直流输电系统中,强大的直流电流流经接地极注入大地时,会在极址土壤中形成一个恒定的直流电流场,因此会出现大地电位升高。进而,当地面跨步电压和接触电势等超过允许值的情况下会带来一系列危害。因此,了解接地极在三维地电环境下产生的电位分布十分有必要。计算了水平圆环形接地极在均匀半空间条件下的电位解析解,并采用有限差分法实现三维复杂地电模型下接地极电位数值模拟。最后,通过建立简化的大地三维电阻率数学模型,如高低阻水平层状或半层状模型、与源距离不同三维高低阻长方体模型、下边界不断延伸的三维低阻长方体模型、高低阻倾斜或直立断裂构造模型等带入程序模拟得到相应的电位分布,从而分析各种模型对电位分布的影响,以期对极址的选择提供参考。

In long distance HVDC transmission system, powerful DC current injected into earth through grounding electrode will form a constant DC electric field in soil, leading to earth potential rise, bringing about a series of harms because step voltage and contact potential will exceed permitted values. So it is necessary to understand potential distribution around grounding electrode in various 3-D geoelectric models. This paper deduced analytical expressions of grounding electrode potential in homogeneous half space. On this basis, by combining with 3D finite difference method, numerical simulation of grounding electrode potential in complex 3-D geoelectric model was realized. Then various geoelectric models similar to actual environment were established, such as horizontal infinite-stratified or semi-infinite-stratified models of high or low resistivity, 3-D high or low resistivity cuboid models, 3-D low resistivity cuboid models with its lower boundary extending continuously, and inclined or vertical fracture structure models of high or low resistivity and so on. Those models were brought into program of numerical potential simulation calculating potential distribution around grounding electrode. Finally, influence of various models on potential distribution was analyzed to provide reference for grounding electrode site selection.